Fiber-reinforced composite materials are used as lightweight and high-strength materials. A fiber-reinforced composite material has a plurality of reinforced fiber bundle layers. Each of the reinforced fiber bundle layers is formed by arranging a plurality of fiber bundles, each of which is formed by bundling fibers. The fiber-reinforced composite material is formed by impregnating, with matrix resin, reinforced fiber base material including the laminated reinforced fiber bundle layers. For example, Patent Documents 1 and 2 disclose fiber base materials as reinforced fiber base materials, in which fabric layers are laminated. Each of the fabric layers is configured by weaving warp threads (first reinforced fiber bundles) and weft yarns (second reinforced fiber bundles) by plain weave, twill, satin weave, and the like.
The fabric base material of Patent Document 1 is formed by alternately laminating, for example, fabric layers each including warp threads oriented at 0 degrees and weft yarns oriented at 90 degrees and fabric layers each including warp threads oriented at +45 degrees and weft yarns oriented at −45 degrees. This easy manufacturing method allows the fabric base material to have quasi-isotropy. Thus, the fabric base material of Patent Document 1 is excellent in manufacturing costs and productivity.
The fabric base material of Patent Document 2 is formed by piling fabric layers (obliquely-crossed fabric layers) while shifting by 45 degrees. Each fabric layer includes warp threads and weft yarns crossing at the narrow angle of 45 degrees, i.e., at the wide angle of 135 degrees.